Supporting spacer for annular corrugated fins



Oct. 26, 1954 s. HOLM SUPPORTING SPACER FOR ANNULAR CORRUGATED FI Filed March 8, 1952 Patented Oct. 26, 1954 SUPPORTING SPACER FOR ANNULAR' CORRUGATED FINS Sven Holm, Wellsville, N. Y., assignor to The Air Preheater Corporation, New York, N. Y.

Application March 8, 1952, Serial No. 275,505

Claims. '1

This present invention relates to heat exchange apparatus and particularly to extended surface for tubes or the like through which one fluid is circulated in heat exchange relationship with another.

Numerous heat exchangers have been proposed in which one fluid is confined to a determined path flow as by directing it through the annular space between a pair of concentric tubes while the other fluid fiows through the smaller of the concentric tubes. To increase the efficiency of heat transfer between the fluid flowing in this tube and that traversing the aforesaid annular passage, longitudinal fins are frequently provided on the tubes with the fins extending radially in good heat transfer relationship with one or both tubes.

In one proposed method of providing such a heat exchange element with extended surface it has been proposed to corrugate a sheet and insert it with the corrugations extending longitudinally of the tubes in a radial position between the inner and outer tubes and with the crests and dwells of the corrugations in contact with these two tubes. To obtain a good heat transfer both without welding or brazing it has been proposed to physically expand the inner of the two tubes after the corrugated fin has been mounted in the annular space and to enable this to be done it has been suggested that a metal should be used for the fin which is not distortable.

It has nevertheless been found most diflicult in practice to expand the inner tube to wedge the corrugated fin into contact with both inner and outer tubes without effecting some distortion of the folds of the corrugated fin. The present invention contemplates the provision of supporting sleeves or collars mounted in cooperative relation with the folds of the fin so as to sustain and render it more rigid.

The invention will be best understood upon consideration of the following detailed description of the illustrative embodiments thereof when read in conjunction with the accompanying drawings in which:

Figure 1 is a perspective view of a portion of a tubular heat exchange element embodying the present invention;

Figure 2 is a transverse sectional view of an earlier form of heat exchange unit comprising a pair of concentric tubes with radial fins in the annular space through which one fluid flows in heat exchange relationship with another traversing the interior of the smaller tube;

Figure 3 is a partial view similar to Figure 2 2 showing the effect of expansion of the inner tube on the folds of the corrugated fin when the inner tube is expanded to wedge the crests and dwells of the fin element in good physical contact with the tube surfaces;

Figure 4 is a fragmentary longitudinal sectional view corresponding to Figure 2;

Figures 5 and 6 show alternative forms for the supporting and reinforcing sleeve associated with the corrugated fin.

In Figure 1 there is shown a form of heat exchanger in which one of the fluids passes through the interior of a tube It in heat exchange relationship with another fiuid that flows in the annular space I I defined by a second tube i2 concentric with the tube IIl. One form of extended surface for a heat exchanger of this type comprises a corrugated sheet [3 bent to circular form and fitted into the annular space i I with the outer faces of the crests I4 and dwells I5 of the corrugations in contact with the confronting cylindrical surfaces of the tubes Ill and I I. The corrugated elements I3 extend longitudinally of the annular passage II and the folds It of the corrugated element extend radially from the inner tube II] to the outer tube I2. To obtain a good physical heat transfer contact between the fin element I3 and the walls of the tubes Ill and I2 it has been proposed heretofore to expand the inner tube Ill (Figure 2) as by means of a mandrel so as to exert a thrust in a radially outward direction on the folds I5 on the corrugated element I3. It has also been proposed that the fin element I3 be made of a suitable metal such that the folds I6 would not buckle or become distorted in their major portions clue to the exertion of the radial force imposed thereon by expansion of the tube l0. Nevertheless, it has been found that in addition to some distortion of the crest and dwell portions I l, I5 of the corrugations to wedge them against the surfaces of the tubes I0 and I2, the radial force resulting from expansion of the tube I0 produces distortion of the folds I6 that extend radially and also causes some displacement of them in a circumferential direction as illustrated in Figure 3.

Considerable difliculty has been experienced in preventing the fin section from deflecting when the inner tube is expanded. This condition is shown in Figure 3. It is obvious that the contact pressure desired is not obtained unless the fin sections are kept in a substantially radial position.

The invention as illustrated in Figure 1 is an improvement in the construction of a finned tube shown in Figures 2 and 3 and contemplates preventing the fin sections I3 from deflecting. In forming the fin sections I3 there is a limit to length that can be formed so that in a long tube several sections are required as shown in Figure 4. In sliding the fin sections I3 into the annular space H, a serrated ring 20 asshown in Figures 4 and 6 is placed between each section I3 and after completing the tube, one or more prongs 23 on the outside rings 25 (Figure 5) are bent and brazed to the inner tube It]. This is shown at 21; in Figure 4. The prongs 23 of ring '25 are tapered so as to have a wedge effect between the folds I6 of fin elements I3. The ring has serrations 2| of a width slightly greater attheir ends than the thickness of fin material. The serrated ring 20 should preferably be placed between sections I3 and pronged ring at each end.

In accordance with the present invention distortion of the fin elements I3 is prevented by providing this collar or sleeve 20 which is pr0- vided with serrations. :2! on its circumferential edges as shown in Figure 6.0r with prongs 23 as shown in Figure 5. Theprongs 23 are spaced so that they fit snugly between the folds I6 of the corrugated element I3 in the plane in which.

the ring 25 is mounted. Asis-more clearly shown in Figure 4, the rings or sleeves 2B, 25 are slight ly larger in diameter than the inner tube II] of the two concentric tubes so that the serrations 2| or .prongs 23 become inserted between the folds I6 of thecorrugated element I3 somewhere near the mid-point of their radial extent. Figure 4 also illustrates that where the fins I3 are interrupted longitudinally of the tube, the serrated sleeve 2|) fits between and mutually interconnects two adjacent fin elements. The pronged sleeves 25 mounted at. the extreme ends of the fin elements at the outer ends of the tubes have some of the prongs bent into contact with the surface of the tube I0 so that they may be brazed thereto asshownat24 in Figure 2.

What I claim is:

1. In a heat exchanger having apair of tubular members spaced in concentric relation to form an annular fluid passage; a'heat transfer fin member in said passage comprising; a sheet member formed. with a .-plurality of generally rectangularcorrugations and bent to circular form with the corrugationsextending parallel to the axis of said tube and the yokes or webs thereof between the side faces of the folds of the corrugations in contact with one or the other of said tubes and the said face portions extending radially between said tubes as fins; and a collar having circumferentially extending edges serrated with the teeth or serrations fitting in the intervals between the folds of said corrugated sheet to maintain the said face portions thereof properly circumferentially spaced and in radially extending relation between said tubes.

7 2. A heat exchanger as recited in claim 1 wherein said collars are serrated on both circumferential edges to engage between a pair of corrugated members on said tubes.

3. In: a heat exchanger having a plurality of concentric tubular members nested to form an annular fluid passage; heat transfer fin member in said passage comprising a corrugated sheet member formed with a plurality of generally rectangular corrugations and bent to circular form with the corrugations extending parallel to the axis of said tube and the yokes or webs between the folds or longitudinal faces of the corrugations in contact with one or the other of saidtubes and the fold .portionsextending radially between said tubes; and a sleeve mounted at each end. of said corrugated member adjacent the tubular member, said sleeve having a serratedzcircumferentially extending edge with the teeth or serrations fitting in the intervals be tween; the folds of said corrugated member to maintain the folds properly circumferentially spaced'between the tubular :members and in radially' extending relation between said tubes.

4. A heat exchanger as recited in claim 3 wherein the-teeth-on said serrated collar are disposed in a circle having a diameter suflicient- 1y greaterthanthatiof the smaller of said tubular members-as to engage between-folds of a corrugated member on said tubular member so as to causezalternate :teeth' to engage the outer faces of the alternateyokes of the corrugations which are in engagement with said smaller tubular member.

5. A. heat. exchanger as recited in claim 3 wherein. said serrated collars. have .convergently tapered teeth that at their roots are of somewhat greater width than the yoke portions of the corrugation folds between whichtheyengage so as to wedge, therebetween.

References Cited; in. the filerof this patent UNITED STATES-PATENTS Number Name Date 2,206,826 Hooper July 2, 1940 2,413,179 Grandmontetal. Dec. 24, 1946 2,594,931 Jaeschke Apr. 29; 1952 

